Xiao, Manda = 金納米晶修飾的空心介孔二氧化矽微球在表面等離子體激元調製下的光散射行為 / 肖蔓達. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Abstracts in English and Chinese. / Xiao, Manda = Jin na mi jing xiu shi de kong xin jie kong er yang hua xi wei qiu zai biao mian deng li zi ti ji yuan diao zhi xia de guang san she xing wei / Xiao Manda. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.iv / Table of Contents --- p.vi / List of Figures --- p.viii / List of Tables --- p.x / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Plasmonic Properties of Noble Metal Nanocrystals --- p.1 / Chapter 1.2 --- Light Scattering from Dielectric Spheres --- p.6 / Chapter 1.3 --- Motivations and Outline of the Thesis --- p.9 / Chapter 2 --- Characterization Techniques --- p.17 / Chapter 2.1 --- Instrumentation --- p.17 / Chapter 2.2 --- Extinction Measurement of Au Nanocrystals and the HMSMSs Decorated with the Au Nanocrystals --- p.17 / Chapter 2.3 --- Sample Preparation for the TEM and SEM Characterization --- p.18 / Chapter 2.4 --- Dark-Field Imaging and Spectroscopy of the Individual Microspheres --- p.19 / Chapter 3 --- Fabrication of Hollow Mesoporous Silica Microspheres Decorated with the Au Nanocrystals --- p.25 / Chapter 3.1 --- Preparation of the Hollow Mesoporous Silica Microspheres --- p.25 / Chapter 3.2 --- Growth of the Au Nanocrystals --- p.29 / Chapter 3.3 --- Assembly of the Au Nanocrystals onto the Hollow Mesoporous Silica Microspheres --- p.32 / Chapter 4 --- Resonant Scattering Properties of the Hollow Mesoporous Silica Microspheres --- p.38 / Chapter 4.1 --- Experimental Results --- p.38 / Chapter 4.2 --- Calculation of the Scattering Spectra by Mie Theory --- p.42 / Chapter 4.3 --- Summary --- p.46 / Chapter 5 --- Resonant Scattering Properties of the Au Nanocrystal-Decorated Hollow Mesoporous Silica Microspheres --- p.49 / Chapter 5.1 --- Effect of the Plasmon Resonances of the Au Nanocrystals on the Resonant Scattering Behaviors of the HMSMSs --- p.49 / Chapter 5.2 --- Estimation of the Scattering Enhancement Factors --- p.54 / Chapter 5.3 --- Summary --- p.59 / Chapter 6 --- Summary --- p.61

Le design de complexes luminescents hétérobimétalliques a suscité un intérêt croissant ces dernières années en raison de leurs propriétés photophysiques uniques. Dans ces complexes de Nd (III) ou Yb (III) associés à des chromophores du bloc d, la forte émission du métal de transition dans le visible est utilisée pour sensibiliser de façon efficace les niveaux f-f du lanthanide(III) qui émet à son tour dans le visible ou l'IR selon la terre rare. Plus spécifiquement l'attention s'est focalisée sur le développement de complexes hétérobimétalliques d-f pour l'émission dans le proche infrarouge (NIR). En effet le proche infrarouge, comparé à l'UV, pénètre plus facilement les tissus biologiques humains notamment la peau. Bien que de telles propriétés confèrent à ces complexes bimétalliques un fort potentiel pour le diagnostic médical, aucun complexe hétérobimétallique d-f greffé de façon covalente à une matrice de silice n'a été décrit. Dans ce travail de nouveaux complexes hétérobimétalliques d-f contenant des ligands silylés ont été préparés et greffés sur la silice. Les complexes monomères [Ru(bpy)2(bpmd)]Cl2 (noté Ru), [Ru(bpy)(bpy-Si)(bpmd)]Cl2 (noté RuL) et [Ln(TTA-Si)3] (noté LnL3) et les complexes hétérobimétalliques d-f Ru-LnL3 et Ln-RuL (Ln = Nd3+, Yb3+) ont été préparés. La caractérisation des complexes a été effectuée par spectroscopie Raman, RMN 1H et 13C RMN. Les spectres RMN 1D 1H et 13C NMR ainsi que 2D de corrélation HSQC confirment les structures proposées. L'étude des propriétés photophysiques met en évidence l'émission de l'élément lanthanide dans le proche infrarouge ainsi que l'efficacité du processus de transfert d'énergie Ru-Ln qui est facilité par le ligand (2,2'-bipyrimidine). Les mesures de durée de vie et de rendement quantique (ΦET) pour le transfert d'énergie indiquent des valeurs remarquables comprises entre 30 et 84 %. La valeur du rendement quantique (ΦET) du complexe d'Yb-RuL, 73,4 %, est à ce jour la plus grande valeur rapportée pour un complexe hétérobimétallique Ru (II)-Yb (III). Le greffage sur différentes matrices de silice, mésoporeuse SiO2 ou dense SiO2 d, a été réalisé. Les nanohybrides SiO2-RuL, SiO2-NdL3 et SiO2-YbL3 ont été obtenus avec des taux de greffage allant de 0,08 à 0,18 mmol de complexe par gramme de silice. [...] / The design of heterobimetallic luminescent complexes has gained growing interest in recent years due to their unique photophysical properties. More specifically, the development of heterobimetallic complexes using d-block chromophores to sensitize the near-infrared (NIR) emission of lanthanide complexes (such as Nd(III) and Yb(III)) has received significant attention taking into account their longer emission wavelengths and the interest of the NIR emission which penetrates human tissue more effectively than UV light. These properties give them potential applications in medical diagnostics or biomedical assays. Transitions to excited state levels of transition metal complexes occurring in the visible and characterized by large absorption coefficients, could efficiently sensitize f-f levels of Ln(III) ions. In this work new d-f heterobimetallic complexes containing silylated ligands were prepared supported on silica materials. [Ru(bpy)2(bpmd)]Cl2 (labeled Ru), [Ru(bpy)(bpy-Si)(bpmd)]Cl2 (labeled RuL) and [Ln(TTA-Si)3] (labeled LnL3) and d-f heterobimetallic complexes, Ru-LnL3 and Ln-RuL (Ln = Nd3+, Yb3+) were prepared. Structural characterization was carried out by Raman Scattering, 1H and 13C NMR spectroscopies. Results obtained from 1H-13C HMBC and HSQC correlation NMR spectra confirm the formation of proposed complexes. Photophysical properties studies highlight the efficiency of Ru-Ln energy transfer processes in NIR-emitting lanthanide complexes mediated by conjugated bridging ligand (2,2'-bipyrimidine). Lifetime measurements were carried out and values of quantum yield for energy transfer (?ET) between 30 and 84 % could be evaluated. ?ET of 73.4 % obtained for the Yb-RuL complex is the largest value reported for Ru(II)-Yb(III) heterobimetallic complexes so far. Grafting on different silica matrix was also demonstrated. SiO2-Ru, SiO2-NdL3 and SiO2-YbL3 nanohybrids were obtained with grafting efficiencies from 0.08 to 0.18 mmol g-1 of silica.[...]

Les azaphosphatranes sont des entités relativement peu utilisées en catalyse organique. Cependant, ils se sont révélés être de bons catalyseurs pour la réaction de couplage entre des époxydes et le dioxyde de carbone pour former des carbonates cycliques. Les travaux de cette thèse portent sur l'optimisation de la réactivité des azaphosphatranes pour la synthèse de carbonates cycliques. Tout d'abord, une étude du confinement à différentes échelles a été réalisée. Les catalyseurs ont été étudiés en présence de silice mésoporeuse de type SBA-15 qui exacerbent leur activité. L'ajout d'un solvant ou de silice entraîne des modifications de mécanisme. La synthèse d'azaphosphatrane encagé au sein d'hémicryptophane a permis d'étudier l'effet d'un double confinement au sein d'une macromolécule et d'un matériau. Ensuite, les azaphosphatranes ont été fonctionnalisés à différentes positions par des groupements activateurs de l'époxyde ou du dioxyde de carbone. Enfin, différentes approches de synthèse de carbonates cycliques énantioenrichis ont été testées. La chiralité a été introduite par le biais de centres asymétriques sur les bras de l'azaphosphatrane ou par le confinement au sein d'un hémicryptophane chiral. Des silices chirales obtenues soit par empreinte moléculaire de proline ou par greffage covalent d’organosilanes chiraux ont également été testées. / Azaphosphatranes have rarely been applied as organocatalysts in organic transformations. Nevertheless, they have recently proved to be efficient single-component metal-free catalysts for the production of cyclic carbonates from epoxides and carbon dioxide. The goal of this work is to optimize the reactivity of azaphosphatrane based catalysts towards greater CO2 fixation into cyclic carbonates. First, they have been used in conjunction with mesoporous silica of the SBA family. A positive synergy, depending on the nature of the counter-anion, was demonstrated leading to better yields in cyclic carbonates. Adding a solvent or silica was shown to drive to a change in the reaction mechanism as evidenced by kinetic studies. Then, different activating functional groups were introduced at different position of the catalyst structure to further activate epoxide or carbon dioxide substrates. Finally, the kinetic resolution of racemic epoxides in the presence of CO2 was investigated. Different approaches to chiral induction have been explored including the introduction of asymmetric carbons on azaphosphatranes, the use of induced chirality with cyclotriveratrylene unit in hemicryptophane moiety. Chiral imprinted with amino acids and chiral grafted mesoporous silicas have also been studied.

One of the leading causes of death and hospital stays in the United States, myocardial infarction (MI) occurs when coronary blockages lead to downstream ischemia in the myocardium. Following the MI, the heart activates a number of pathways to repair or remodel the infarcted zone. Endothelial cells respond to ischemia by de-differentiating to form neovasculature and myofibroblasts. The resident cardiac differentiable stem cells (CDCs) are recruited via local cytokines and chemokines to the infarct zone where they too differentiate into myofibroblasts. Mesenchymal stem cells (MSCs) of the bone marrow respond to circulating factors by immobilizing to the heart and differentiating down cardiac lineages. In regenerative medicine approaches, these processes are exploited to augment the resident supply of reparative cells. Clinical trials to transplant cardiac stem cells into MI zones have been met with mixed results. When CDCs are harvested from autologous or type-matched donors, the cells are prepared with a minimum of manipulations, but the yield is quite small. Conversely, MSCs from bone marrow are highly proliferative, but the manipulations in culture required to trigger cardiac differentiation have been found to transform the cell into a more immunogenic phenotype. In addition, there is a dearth of in vivo evidence for the fate of transplanted cells. Currently, intracardiac echocardiographs are used to assess the infarcted area and to guide delivery of stem cell transplants. However, this modality is invasive, short-term, and does not image the transplanted cells directly. In this project, I addressed these shortcomings with a regenerative medicine and bioimaging approach. Our lab has developed multimodal nanoparticles based on a core of mesoporous silica, functionalized with fluorescein or tetramethylrhodamine isothiocyanate for visibility in fluorescent microscopy, Gd2O3 for magnetic resonance imaging (MRI), and trifluoropropyl moieties for ultrasound applications. After establishing in vitro models of cardiac stem cells using CDCs and MSCs, the particles were implemented and characterized in vitro. At a concentration of 125 μg/mL in culture, the particles are highly biocompatible, and labeled cells were found to be fluorescent, echogenic, and detectable with MRI in prepared agar phantoms. Ex vivo mouse hearts, first mounted in agar phantoms, then left in situ, were implemented as a model for guided delivery using ultrasound and follow-up cell tracking with MRI. These results in this project demonstrate the feasibility of this highly novel and practical approach. Additional studies will be carried out to evaluate the biocompatibility and retention versus clearance in live animal models, prior to the carrying out of true pre-clinical models for myocardial infarction.

It was recently shown that V-doped acid-prepared mesoporous silica (APMS) nanoparticles are active catalysts for the oxidation of the mustard gas analogue 2-chloroethyl ethyl sulfide (CEES) under ambient conditions in the presence of aldehydes, using O2 from air as the oxidation source. However, the vanadium ion leached from the surface when water was present, leading to decreased catalytic activity. Therefore, in this work, the environment around the vanadium is changed, using diethylenetriamine pentaacetic acid (dtpa) as a ligand and anchoring it to the surface of a mesoporous silica nanoparticle, to investigate its effect on vanadium’s ability to perform oxidation reactions. VO(dtpa)-APMS was synthesized by covalently linking the multi-dentate chelator dtpa onto the surface through peptide coupling of one of the acetate groups to aminopropyltriethoxysilane (APTES), condensing the dtpa-APTES molecule onto the mesoporous silica surface, and then exchanging a vanadyl salt into the resulting solid. Physical characterization of the material confirmed that the substrate retained its porosity after modification, and that the vanadium did not leach from the solid, in contrast to samples that did not contain dtpa. Solid-state EPR spectroscopy, combined with ongoing computational modeling, indicated that the vanadium was in a distorted five-coordinate environment. Various vanadium catalysts have been shown to oxidize alkanes, alkenes, alcohols and aromatic compounds. To further understand the catalyst’s ability to perform oxidation reactions, mechanisms of sulfides and alkenes were studied. Two model substrates were chosen for the investigation: CEES and cis-cyclooctene. The catalytic system effectively oxidizes CEES at room temperature in less than 15 minutes and cis-cyclooctene at 47 °C within 3 hours, using a peroxyacid generated in situ as the oxidant source. Kinetic experiments demonstrated that the mechanism of the sulfide reaction changed at higher temperatures, while the alkene reaction did not. In each reaction, a partial negative charge on the peroxyacid during the oxidation process was indicated. The confirmation of radical formation in the mechanism was experimentally shown by the appearance of an induction period when diphenylamine, a radical trap, was introduced into the reaction. VO(dtpa)-APMS performs two catalytic oxidations: the oxidation of propionaldehyde to make the peroxyacid and the oxidation of alkenes or sulfides. In the first reaction, O2 binds to the vanadium complex to form a superoxo eta-1-bound O2 radical. This species leads to the formation of peroxyacid through a radical process. The peroxyacid produced in this manner can then react with a sulfide or an alkene in a process also catalyzed by the VO(dtpa) complex. The peroxyacid coordinates with the vanadium center. Upon coordination, the sulfide or alkene directly reacts with the oxygen of the peroxyacid while the peroxyacid is being deprotonated. A 6-coordinate catalyst intermediate is formed prior to the release of the oxidation product and propionic acid to regenerate the VO(dtpa) complex.

L’interface entre deux solutions électrolytiques immiscibles (ITIES) peut agir comme un support pour l’assemblage de nanoobjets. Cela présente de nombreux avantages : les particules ne requièrent pas d’ingénierie particulière pour leur obtention, peuvent s’assembler dans des conditions qui leur sont propres, sont pratiquement non dégradables et facilement renouvelables. Les recherches actuelles portent tant sur leur utilisation potentielle en tant que plateformes pour des appareils optiques ajustables, pour des capteurs ou encore pour de la catalyse. L’adsorption de nanoparticules de silice, dense ou mésoporeuse, à l’interface liquide-liquide a été étudiée par voltammétrie en courant alternatif. L’interaction des nanoparticules de silice avec le bleu de méthylène et l’éosine B a été étudiée par voltammétrie cyclique et spectrophotométrie. Les constantes thermodynamiques d’adsorption du bleu de méthylène ont été déterminées à 1.66 105 et 3.68 103 sur les particules de silice dense et mésoporeuse respectivement. La variation de constante entre les deux types de silice repose essentiellement sur leur état d’ionisation respectif. L’énergie de Gibbs de transfert entre phase liquide est modifiée de 8.9 kJ mol-1 en présence de nanoparticules denses ce qui donne des indications sur le mécanisme de transfert du bleu de méthylène en présence de nanoparticules. Mettant à profit l’aptitude de la silice à accumuler le bleu de méthylène et à s’adsorber sur l’interface liquide il nous a été possible d’améliorer la sensibilité de la détection électrochimique. L’éosine B n’a aucune interaction avec les particules de silice. Nos efforts ont ensuite porté sur l’amélioration de la sélectivité du transfert électrochimie par l’utilisation de nanoparticules de silice à empreinte moléculaire. Des nanoparticules de silice dense à empreinte moléculaire de Diclofénac (DIN) ont été synthétisées. Cette molécule est un anti-inflammatoire non stéroïdien très largement utilisé et figurant sur la liste européenne des polluants émergents. Les constantes d’affinité du Diclofénac pour les DIN et les particules équivalentes sans empreinte sont de 7.47 108 et 2.96 107 respectivement ce qui démontre clairement la présence d’empreintes ayant une forte affinité pour le diclofénac au sein des particules. Des molécules analogues (Diclofénac acide, Aceclofenac, acide 4 phenyl-azo benzoique) ont été testées et ont une affinité faible pour les DIN. En électrochimie, l’ajout de DIN bloque le transfert de Diclofénac à l’interface liquide-liquide / The interface between two immiscible electrolyte solutions (ITIES) can act as a scaffold for the assembly of nanometer-sized objects. The assembly of nanoparticles at liquid-liquid interfaces has numerous advantages – the nanoparticles do not require engineering, can assemble given proper conditions, are practically non-degrading and easily renewable. Research is ongoing into their use as a platform for tunable optical devices, sensors and catalysis. The adsorption of both dense and mesoporous silica nanoparticles at the ITIES was studied by AC voltammetry. Their interactions with methylene blue (MB+) and Eosin B (EB-), selected as a model ions, were studied by cyclic voltammetry and UV/Vis absorption spectroscopy. The thermodynamic constants of adsorption of MB+ were found to be 1.66 105 and 3.68 103 onto dense and mesoporous silica nanoparticles respectively. The difference of adsorption constants for the two types of silica was explained by their differing ionisation states. The Gibbs energy of transfer of MB+ is shifted by -8.9 kJ mol-1 in the presence of dense silica nanoparticles, giving some insights to the transfer mechanism of MB+ in presence of nanoparticles. Combining the ability of silica to adsorb onto the ITIES and their affinity for MB+, MB+ was accumulated at the ITIES and so an increase in sensitivity of electrochemical detection was achieved. Eosin B demonstrated no affinity for the silica nanoparticles and its transfer at the ITIES was not influenced by their presence. Next the focus was placed on improving the selectivity of the interaction by synthesising imprinted silica nanoparticles, more specifically, Diclofenac-imprinted dense silica nanoparticles. This drug was chosen as it is a commonly used nonsteroidal anti-inflammatory drug which has been placed on the European watch list of emerging pollutants. The thermodynamic constants were calculated as 7.47 108 for Diclofenac-imprinted silica and only 2.96 107 for non-imprinted silica. Thus the presence of imprint cavities greatly influences the affinity of diclofenac for the silica nanoparticles. The analogues of Diclofenac (Aceclofenac, Acid diclofenac, 4-phenyl azo benzoic acid) were shown to have a very limited affinity for the imprinted particles. Electrochemical experiments at the liquid-liquid interface revealed that the diclofenac transfer is blocked by the presence of imprinted particles

Encapsulation of biomolecules is of great interest to research advances related to biology, physiology, immunology, and biochemistry, as well as industrial and biomedical applications such as drug delivery, biocatalysis, biofuel, food and cosmetics. Encapsulation provides functional characteristics that are not fulfilled by free biomolecules and stabilizes the fragile biomolecules. In terms of biocatalysis, solid support can often enhance the stability of enzymes, as well as facilitate separation and recovery for reuse while maintaining activity and selectivity. Various kinds of materials have been used for encapsulation of biomolecules, among which, porous materials are an important group. Metal-organic frameworks (MOFs) have attracted much attention and emerged as a new generation of highly porous functional materials with potential in a variety of fields such as gas separation and storage, catalysis, sensors and biomedical applications. Their structural versatility and amenability to be designed with specific functionality, together with their extra-large surface areas confer them a special place amongst traditional porous materials. In particular, because ligands can be designed with particular organic functional groups for specific interactions with biomolecules, they are attractive in the stabilization and retention of enzyme/proteins for biomedical or biocatalysis applications. With enlarged pore sizes, mesoporous (pore sizes in the range of 2 to 50 nm) MOFs are of great interest in the encapsulation of proteins. In this dissertation, I am focusing on the encapsulation of biomolecules into mesoporous MOFs (mesoMOFs) to estabilish the biomolecules@mesoMOF platform, including synthesis, characterization and mechanistic studies of a series of novel biomolecules@mesoMOF materials, and to develop the biomolecule@mesoMOFs platform for various applications.

Confining walls induce qualitative changes in adsorbed fluids. Among the most intriguing phenomena is hysteresis, where a pore fills with fluid at a greater pressure than it empties. The causes and mechanisms by which this occurs are intensely investigated yet still poorly understood. Ordered mesoporous silicas, recently discovered materials with well-defined pore size distributions, provide an opportunity to deepen our understanding of the fundamental physics of the interaction of fluids with complex solids.In part of this computational investigation we examine idealized pores. In agreement with other recent studies, we find that in 'inkbottle'-shaped pores, where a large cavity is accessible to the bulk fluid only by constrictions, there is no evidence of the long-hypothesized phenomenon of `pore blocking', where the constrictions inhibit fluid desorption from the cavity. We find that even in these simple systems the mechanism of hysteresis depends on pore characteristics, fluid properties and external conditions.For silicas containing cylindrical holes of nearly uniform diameter, such as MCM-41, the state-of-the-art is to consider only a single pore, but the poor qualitative agreement of theoretical with experimental results has improved little as wall representations of increasing sophistication have been developed. Using only a one-dimensional potential, we reproduce features of isotherms, including in the hysteresis region, by averaging over a narrow distribution of pore sizes. The qualitative behavior is shown to be a collective phenomenon not representative of any individual pore. Adding surface roughness and a constriction to the pores yields results quantitatively nearly indistinguishable from experiments.For materials larger than MCM-41, a continuum simulation proves too computationally taxing. Thus, a lattice model with adjustable fineness of site spacing is developed. It is found that a surprisingly low level of fineness is needed for confined systems to closely approximate continuum results. This model is applied to cubically symmetric materials, such as MCM-48 and SBA-16, finding that simulations are able to reproduce much of the qualitative behavior seen experimentally, but the lack of existing knowledge of the nature of silica walls proves to be a limiting factor.

Mesoporous thin films are promising architectures for positive electrodes in Li-ion battery applications. A particular challenge in this field has been successful templating of vanadium-based oxides, materials known for their ability to host lithium, since their thermal instability and complex vanadium chemistry hinder templating through traditional soft-chemistry approaches. To address these technical problems we here develop the soft-templating of vanadium and niobium mixed oxides based on Evaporation Induced Micelles Packing using thermally stable polystyrene-b-polyethyleneoxide structuring agents. In-situ thermal monitoring via ellipsometry allows successful navigation of the thermal stability landscape. TEM and AFM analyses reveal homogeneous wormlike mesoporous structures whose pore and inorganic wall sizes can be tuned from 15 to 100 nm by changing the hydrophobic/hydrophilic surfactant chain lengths. Ellipsometric porosimetry shows that 100 nm thick films with a 15 nm pore size displays 30% electrolyte accessible porosity. The interconnected tridimensional mesoporous network has been highlighted by electronic tomography. Thicker films up to 1.3 µm are prepared by a multidipping process. The superiority of such nanoarchitectures compared to non porous materials in terms of electrochemical properties such as capacity are revealed using cyclic voltammetry.

This dissertation has been focused on the synthesis and characterization of novel functionalized silica mesoporous crystals by using cationic surfactant and co–structure directing agents (CSDA), the central concept of the synthesis method is to build proper organic/inorganic interactions by introducing CSDA into the synthesis system. By using cationic surfactant as template and anionic CSDA, carboxylic group functionalized mesoporous silicas were successfully synthesized. Well ordered 2D p6mm, cubic Fm-3m, mixture of CCP (Fm-3m) and HCP (P63/mmc), and cubic Fd-3m with uniform carboxylic group distribution have been obtained. Besides, we have investigated the Fm-3m/Fd-3m type intergrowth and new type defects observed in the Fd-3m structure using transmission electron microscopy (TEM) and proposed a “polyhedron packing” model. New amphoteric, inorganic amino acid with highly ordered mesopores were synthesized. Uniform distribution of acid and base organic groups on the mesopore surfaces were formed by interactions between the counter charged surfactant head groups and ionic parts of CSDAs. It has been demonstrated that organic (–NH2 and –COOH) pairs incorporated in the mesopore walls behave as natural amino acids, collectively exhibiting an isoelectric point of ~6.0. Moreover, we have demonstrated that the inorganic amino acid is an efficient catalyst for the reaction between aldehydes and carbon nucleophiles.